Boris Johnson has announced that, the time being right, the stars in alignment and Dave having been dispatched by a bus driven by Tory rebels, he would like “a crack” at being prime minister. It is all rapped up in a cosy rugby metaphor: something about balls and scrums, thus sounding unthreatening while announcing vaulting ambition.

The shrewd TV decoder of politicians’ myths, Michael Cockerell, has wormed out of the Mayor that he would like to be leader of the dear old party and, if possible, the country. Tellingly, Boris allows himself the deflationary let-out clause that it’s “not going to happen”, just in case it doesn’t.

Evasions are part of the craft of politics. But as a contemporary of Mr Johnson at university — we are Generation Bozza — I see a trend repeating itself. He was an outstanding president of the Union debating society while I was editor of the university paper, pumping out exciting headlines like “Spare us the Cutter”, to mark the visits of Tory ministers and (bizarrely) a campaign against irradiated foods, which oddly failed to catch the public imagination.

Mr Johnson, an adept self-publicist even then, invited us round to unveil his list of speakers for the coming term over sherry in the Union library. It all felt impossibly grown-up. His list seemed fine but not overwhelming by the driving standards of the university parish paper. “Is that it?” I blurted. The crestfallen expression on his face was touching. To this day, I get the impression that not being adored, even for a minute, bothers Bozza a lot.

Even worse is someone else being adored in preference. Hence the stinging line in the documentary of his memories of the present prime minister, when they were both at Eton. “Someone said, ‘There’s a Cameron minor’, and there was this tiny little chap.” It’s all very Jennings and Darbyshire but with live ammo.

When Cameron scales the greasy pole this naturally major-minor order is a bit upset. Mr Johnson has thus worked hard as a gifted journalist, humorist and mayor, using London to create a springboard for a leadership bid. In that role, he is beginning, however, to look a bit more like a serious politician with beliefs as well as opportunistic quirks. He is, for instance, one of the few senior Tories to face down his party on immigration, having a better understanding than many on his own side of the open culture that countries need in order to thrive in the global market for talent and competition between cities.

And beneath the rah-rah Eurosceptic knockabout which so easily fools the Tory troops is a realist who wouldn’t quit the EU, banana bans and all. Alas, he has little control over whether all this comes to fruition. The best he can do is wait to see if the rugby ball comes skidding towards him — or sails away towards some quietly ambitious member of the 2010 intake.

Bozza is often described as super-confident and “comfortable in his own skin”. I wonder. Never underestimate the ambition our Oxford of the late Thatcher years bred into us, underpinned in the Mayor’s case by those years vying for precedence in the Etonian sandpit. The real drive is a fear of failure, with a nimble joke to conceal the anxiety that it might not work out.